The present invention relates to an elevator ascending and descending at a high speed and, more particularly, to structures of a car of an elevator for reducing a noise by means of fairing.
2. Description of the Related Art
Recently, as multi-storied buildings to be built have been heightened, the higher acceleration of elevators to be installed in such buildings have also been proceeded. When the speed of elevator car is accelerated faster than approximately 400 m/min, unpleasant noise in the car is increased. The noise in the car at the low speed is known heretofore mainly caused by vibration noise. On the other hand, it is indicated that in the case of the noise in the car at high speed, "aerodynamical noise" essentially including air flow noise due to vortex generated around the car becomes larger than the vibration noise.
One of conventional elevators will be described with reference to FIGS. 13A and 13B and the state of air flows generated around an elevator car will be described.
FIG. 13A is a schematic perspective view of a conventional elevator, and FIG. 13B is an explanatory view showing the state of air flows around the elevator. In FIGS. 13A and 13B, a conventional elevator mainly has a rectangular parallelepiped elevator car 1 disposed vertically movably in a duct provided in a building or the like, a car entrance/exit front wall 2 provided with a car entrance/exit 4 to be opened or closed by a door 3, and sidewalls 5. Further, an apron 6 is mounted at the lower section of the opening wall 2. The apron 6 has a width wider than the width of the entrance/exit 4 for keeping passenger's safety to ride on or alight from the car, and is formed of thin plate having a length of about 1/2 of the height of the car and mounted to extend downwardly in the vertical direction. Further, a rope 7 and guide rails 8 are provided. The rope 7 is fixed at one end to the car 1 and provided at the other end with "a counter weight", and the rope 7 is driven by a hoisting device (not shown) to vertically move the suspended car 1 along the guide rails 8.
In the conventional elevator constructed as described above, if the car is operated upwardly and downwardly at the same high running speed such as, for example, 420 m/min., larger noise is generated at the time of descending of the car 1 as compared with that at the ascending of the car 1, and the noise level in the car 1 is exceeded by several dBA at the time of descending.
It has been heretofore confirmed that there is a difference at the noise levels between the noise generated at the time of descending and that generated at the time of ascending of the car 1 running at high speed. As concerned with this difference the present inventor has further searched in detail and the following facts have been discovered.
In FIG. 13B, when the car 1 descends in a direction of a thick arrow A, the air at the lower side of the outer wall of the car 1 passes a narrow space between the inner wall of the duct and the car 1 to move to the upper side of the car 1. At this time, vortexes 9 of "horseshoe shape" flowing to enclose the side surface of the car 1 from the lower side are generated in the air flow flowing at the outside of the car 1. It was also confirmed that streamwise vortexes 11 flowing around the side edge 10 extending downstream (upward in the figure) are generated at the lower arpon 6 of the front wall 2 of the car 1. The vortexes 9 of the horseshoe shape extending downstream of the above-described vortexes are normally generated at the air flow around a blunt body. The streamwise vortexes are generated from the fact that by the lower extension plate (apron) extended downwardly the air is stagnated to the lower side of the car so that the air flowed from the lower side of the car to the front surface side of the lower extension plate having lower pressure just to circulate at the side edge. And the streamline of the flow of the air flowing from the back surface side of the lower extension plate is bent by the formation of the streamwise vortexes and forming so-called "contraction flows" and to become local "accelerated flows". The speed of the accelerating flow 12 reached 1.3 times as fast as the running speed of the car 1.
Vortexes 13 of "horseshoe shape" were also generated around guide rails 8 at the sidewalls 5 of the car 1. Further, it has also been discovered that largescale separation bubbles 14 were formed in the vicinity of the sidewalls 5 and the back wall of the car 1 to generate complicated "separation flows".
Since the accelerating flows 12 flow along the front wall 2 having a number of steps such as, the door 3, the entrance/exit 4, a step for riding on or alighting from the car 1 as compared with the sidewalls 5 of the car 1, aerodynamical noise is generated at the front wall 2 due to the steps causing flow disorders. An interval between the inner wall of the duct and the car 1 is narrower than that of the sidewall 5, there is the entrance/exit 4 at the front wall 2, and the entrance/exit 4 is closed by the door 3, but its sealability is not sufficient. Therefore, generated aerodynamical noise is introduced through the interval into the car 1 and enhance the noise level in the car 1. Further, since the front wall 2 has the entrance/exit 4, the door 3 and a mechanism for opening and closing the door 3, it is difficult to enhance its noise shielding performance. As a result, its riding feeling in the car 1 is deteriorated. Further, on the sidewalls and the back wall where the separation bubbles are formed and generate complicated separation flows, aerodynamical noise is generated from in the vicinity of the reattachement regions of the separation flow, then enhance the noise level in the car similarly to the aerodynamical noise due to the accelerating flows.
Since the aerodynamical noise is increased as the ascending and descending speeds of the car are accelerated, noise reduction is further difficult when the ascending and descending speeds of the car are further accelerated.
More specifically, as a result of the oil flow pattern technique experiment by using a model formed in the shape shown in FIG. 13B, it has been cleared that a number of "turbulence" of the (air) flows as shown in FIGS. 14A to 14C (e.g., vortexes) occurred around the car of the conventional elevator. It has also been discovered from the result of the present inventors' experimental analysis that high speed flows called "accelerating flows" were generated in the front wall of the car.
From these experimental results it is supposed that, the main causes of the internal noise of the car of the conventional elevator car were the above-described "turbulence of the (air) flows" and "accelerating flows".
Elevators constituted by providing various "fairing plates" at the upper and/or lower portions of elevator cars to reduce air flowing noise due to vortexes generated around elevator cars are disclosed in Published Unexamined Japanese Patent Application Nos. Sho 45-32569, 50-102043, Published Unexamined Japanese Utility Model Application Nos. Sho 49-46121 and 60-98751.
However, since vertical vortexes are generated at the side edges of fairing plates due to pressure difference between the front surface and the rear surface of the fairing plate in all the prior arts, it is supposed discovered that "accelerating flows" are generated at the front side, i.e., at the front surface side, and aerodynamical noise due to the accelerating flows are increased in the elevator car as the ascending and descending speeds of the car are accelerated.